KR20190120370A - Method and apparatus for transmitting and receiving reference signal in wireless communication system - Google Patents

Abstract

A method and apparatus for decoding by a terminal in a wireless communication system. According to the present invention, a demodulation reference signal (DMRS) set according to a specific pattern from a base station is received from a base station through a DMRS symbol, and the demodulation reference signal is transmitted on a specific antenna port and is transmitted on another antenna port. Located on the same one or two time axis symbols as at least one other demodulation reference signal, the specific pattern is determined according to a characteristic of a frequency band in which the demodulation reference signal is transmitted, and the demodulation reference signal is one or two. A method and apparatus for mapping a time axis symbol using at least one of a first code division multiplexing (CDM) on a frequency axis or a second CDM on a time axis, and decoding the data using the demodulation reference signal. can do.

Description

Method and apparatus for transmitting and receiving reference signal in wireless communication system

The present invention relates to a wireless communication system, and more particularly, to a method and apparatus for generating and transmitting and receiving a demodulation reference signal (DMRS) for decoding data in a wireless communication system.

Mobile communication systems have been developed to provide voice services while ensuring user activity. However, the mobile communication system has expanded not only voice but also data service.As a result of the explosive increase in traffic, a shortage of resources and users are demanding higher speed services, a more advanced mobile communication system is required. have.

The requirements of the next generation of mobile communication systems are to support the massive explosive data traffic, the dramatic increase in the data rate per user, the large increase in the number of connected devices, the very low end-to-end latency, and the high energy efficiency. It should be possible. Dual Connectivity, Massive Multiple Input Multiple Output (MIMO), In-band Full Duplex, Non-Orthogonal Multiple Access (NOMA), Super Wideband Various technologies such as wideband support and device networking have been studied.

An object of the present invention is to provide a method and apparatus for generating and transmitting a demodulation reference signal (DMRS) for decoding data.

Another object of the present invention is to provide a method and apparatus for generating and transmitting / receiving a DMRS for estimating a Common Phase Error (CPE) / Carrier Frequency Offset (CFO) value due to a Doppler Effect.

Another object of the present invention is to provide a mapping pattern of a demodulated reference signal in consideration of a trade-off between overhead due to transmission of a reference signal and channel estimation performance.

Another object of the present invention is to provide a multiplexing method for extending the number of ports for transmitting a demodulation reference signal.

Another object of the present invention is to provide a method of mapping a reference signal using a code division multiplexing scheme on a frequency axis and a time axis.

Another object of the present invention is to provide a multiplexing method for extending the number of ports for transmitting a demodulation reference signal and a method of repeating the same.

The technical problems to be achieved in the present specification are not limited to the technical problems mentioned above, and other technical problems not mentioned above will be clearly understood by those skilled in the art from the following description. Could be.

Specifically, the decoding method of the terminal according to an embodiment of the present invention, receiving a demodulation reference signal (DMRS) set according to a specific pattern from the base station from the base station through a DMRS symbol, the demodulation The reference signal is transmitted on a specific antenna port and is located on the same one or two time axis symbols as at least one other demodulation reference signal transmitted on another antenna port, and the demodulation reference signal is located on the one or two time axis symbols. Mapped using at least one of a first code division multiplexing (CDM) on a frequency axis or a second CDM on a time axis, wherein the specific pattern is determined according to a characteristic of a frequency band in which the demodulation reference signal is transmitted; And decoding the data using the demodulation reference signal.

Further, in the present invention, the demodulation reference signal is located on the one or two time axis symbols based on at least one of the number of transport layers, the port index, the rank, or the maximum number of transport ports.

In the present invention, when the demodulation reference signal is located on one time axis symbol, the demodulation reference signal is mapped using the first CDM.

In addition, in the present invention, when the demodulation reference signal is located on two time axis symbols, the demodulation reference signal is mapped using the second CDM.

The present invention may further include receiving a signal indicating whether the second CDM is applied from the base station, wherein if the signal indicates the application of the second CDM, the demodulation reference signal is the first CDM. And the second CDM.

The present invention may further include receiving a signal indicating the length of the first CDM from the base station when the first CDM is applied, whether or not the second CDM is applied to the first CDM. It depends on the length.

Also, in the present invention, when the demodulation reference signal is mapped using the first CDM and the second CDM, an orthogonal cover code (OCC) applied to the second CDM is determined by the base station. It is limited to at least one type.

The present invention further includes receiving a signal indicating the at least one type from the base station.

In addition, the present invention, the radio unit (Radio Frequency Unit) for transmitting and receiving a radio signal with the outside; And a processor operatively coupled to the wireless unit, wherein the processor receives a demodulation reference signal (DMRS) set according to a specific pattern from a base station through a DMRS symbol from the base station, wherein the demodulation reference signal Is located on one or two time axis symbols that are transmitted on a particular antenna port and are identical to at least one other demodulation reference signal transmitted on another antenna port, wherein the demodulation reference signal is a frequency axis in the one or two time axis symbols. Mapped using at least one of a first code division multiplexing (CDM) or a second CDM on a time axis, wherein the specific pattern is determined according to characteristics of a frequency band in which the demodulation reference signal is transmitted, and the demodulation reference The signal is on the frequency axis in the one or two time axis symbols A terminal is mapped using at least one of a first code division multiplexing (CDM) or a second CDM on a time axis, and decodes the data using the demodulation reference signal.

According to the present invention, data can be decoded by estimating Common Phase Error (CPE) and Carrier Frequency Offset (CFO) values due to Doppler Effect through DMRS.

In addition, the present invention has an effect of estimating a channel through additional DMRS in a high doppler environment.

In addition, the present invention has the effect of changing the pattern of the DMRS according to the situation of the terminal by mapping the demodulation reference signal in consideration of the trade-off between overhead and channel estimation performance due to the transmission of the reference signal. .

In addition, the present invention has an effect of extending the number of ports for transmitting a demodulation reference by using a code division multiplexing scheme not only on the frequency axis but also on the time axis.

In addition, the present invention has the effect of extending the number of ports for transmitting a demodulated reference signal by mapping the reference signal using multiplexing and repetition.

Effects obtained in the present specification are not limited to the above-mentioned effects, and other effects not mentioned above may be clearly understood by those skilled in the art from the following description. will be.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, included as part of the detailed description in order to provide a thorough understanding of the present invention, provide embodiments of the present invention and together with the description, describe the technical features of the present invention.
1 illustrates a structure of a radio frame in a wireless communication system to which the present invention can be applied.
2 is a diagram illustrating a resource grid for one downlink slot in a wireless communication system to which the present invention can be applied.
3 shows a structure of a downlink subframe in a wireless communication system to which the present invention can be applied.
4 shows a structure of an uplink subframe in a wireless communication system to which the present invention can be applied.
5 illustrates a reference signal pattern mapped to a downlink resource block pair in a wireless communication system to which the present invention can be applied.
6 shows an example of a resource area structure used in a communication system using mmWave to which the present invention can be applied.
7 and 8 illustrate an example of a pattern of a demodulation reference signal proposed in the present specification.
9 to 13 are diagrams illustrating an example of a method of mapping DMRSs using a repeating pattern proposed herein.
14 is a flowchart illustrating an example of a method for generating and transmitting a demodulation reference signal proposed in the present specification.
15 is a flowchart illustrating an example of a method of decoding data by receiving a demodulation reference signal proposed in the present specification.
16 is a diagram illustrating an example of an internal block diagram of a wireless device to which the present invention can be applied.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is intended to explain exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, one of ordinary skill in the art appreciates that the present invention may be practiced without these specific details.

In some instances, well-known structures and devices may be omitted or shown in block diagram form centering on the core functions of the structures and devices in order to avoid obscuring the concepts of the present invention.

In this specification, a base station has a meaning as a terminal node of a network that directly communicates with a terminal. The specific operation described as performed by the base station in this document may be performed by an upper node of the base station in some cases. That is, it is obvious that various operations performed for communication with a terminal in a network composed of a plurality of network nodes including a base station may be performed by the base station or other network nodes other than the base station. A base station (BS) is to be replaced by terms such as a fixed station, a Node B, an evolved-NodeB (eNB), a base transceiver system (BTS), an access point (AP), and a transmitting end. Can be. In addition, a 'terminal' may be fixed or mobile, and may include a user equipment (UE), a mobile station (MS), a user terminal (UT), a mobile subscriber station (MSS), a subscriber station (SS), and an AMS ( Advanced Mobile Station (WT), Wireless Terminal (WT), Machine-Type Communication (MTC) Device, Machine-to-Machine (M2M) Device, Device-to-Device (D2D) Device, Receiver, etc.

Hereinafter, downlink (DL) means communication from a base station to a terminal, and uplink (UL) means communication from a terminal to a base station. In downlink, a transmitter may be part of a base station, and a receiver may be part of a terminal. In uplink, a transmitter may be part of a terminal and a receiver may be part of a base station.

Specific terms used in the following description are provided to help the understanding of the present invention, and the use of such specific terms may be changed to other forms without departing from the technical spirit of the present invention.

The following techniques are code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and NOMA It can be used in various radio access systems such as non-orthogonal multiple access. CDMA may be implemented by a radio technology such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA may be implemented with wireless technologies such as global system for mobile communications (GSM) / general packet radio service (GPRS) / enhanced data rates for GSM evolution (EDGE). OFDMA may be implemented in a wireless technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA). UTRA is part of a universal mobile telecommunications system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of evolved UMTS (E-UMTS) using E-UTRA, and employs OFDMA in downlink and SC-FDMA in uplink. LTE-A (advanced) is the evolution of 3GPP LTE.

Embodiments of the present invention may be supported by standard documents disclosed in at least one of the wireless access systems IEEE 802, 3GPP and 3GPP2. That is, steps or parts which are not described to clearly reveal the technical spirit of the present invention among the embodiments of the present invention may be supported by the above documents. In addition, all terms disclosed in the present document can be described by the above standard document.

For clarity, the following description focuses on 3GPP LTE / LTE-A, but the technical features of the present invention are not limited thereto.

General wireless communication system to which the present invention can be applied

1 illustrates a structure of a radio frame in a wireless communication system to which the present invention can be applied.

3GPP LTE / LTE-A supports a type 1 radio frame structure applicable to frequency division duplex (FDD) and a type 2 radio frame structure applicable to time division duplex (TDD).

In FIG. 1, the size of the radio frame in the time domain is expressed as a multiple of a time unit of T_s = 1 / (15000 * 2048). Downlink and uplink transmission consists of a radio frame having a period of T_f = 307200 * T_s = 10ms.

1A illustrates the structure of a type 1 radio frame. Type 1 radio frames may be applied to both full duplex and half duplex FDD.

A radio frame consists of 10 subframes. One radio frame is composed of 20 slots having a length of T_slot = 15360 * T_s = 0.5ms, and each slot is assigned an index of 0 to 19. One subframe consists of two consecutive slots in the time domain, and subframe i consists of slot 2i and slot 2i + 1. The time taken to transmit one subframe is called a transmission time interval (TTI). For example, one subframe may have a length of 1 ms and one slot may have a length of 0.5 ms.

In FDD, uplink transmission and downlink transmission are distinguished in the frequency domain. While there is no restriction on full-duplex FDD, the terminal cannot simultaneously transmit and receive in half-duplex FDD operation.

One slot includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in the time domain and a plurality of resource blocks (RBs) in the frequency domain. Since 3GPP LTE uses OFDMA in downlink, the OFDM symbol is for representing one symbol period. The OFDM symbol may be referred to as one SC-FDMA symbol or symbol period. A resource block is a resource allocation unit and includes a plurality of consecutive subcarriers in one slot.

FIG. 1B illustrates a frame structure type 2. FIG.

Type 2 radio frames consist of two half frames each 153600 * T_s = 5 ms in length. Each half frame consists of five subframes of 30720 * T_s = 1ms in length.

In a type 2 frame structure of a TDD system, an uplink-downlink configuration is a rule indicating whether uplink and downlink are allocated (or reserved) for all subframes.

Table 1 shows an uplink-downlink configuration.

Referring to Table 1, for each subframe of a radio frame, 'D' represents a subframe for downlink transmission, 'U' represents a subframe for uplink transmission, and 'S' represents a downlink pilot. A special subframe consisting of three fields: a time slot, a guard period (GP), and an uplink pilot time slot (UpPTS).

DwPTS is used for initial cell search, synchronization or channel estimation at the terminal. UpPTS is used for channel estimation at the base station and synchronization of uplink transmission of the terminal. GP is a section for removing interference caused in the uplink due to the multipath delay of the downlink signal between the uplink and the downlink.

Each subframe i is composed of slots 2i and slots 2i + 1 each having a length of T_slot = 15360 * T_s = 0.5ms.

The uplink-downlink configuration can be classified into seven types, and the location and / or number of downlink subframes, special subframes, and uplink subframes are different for each configuration.

The time point when the downlink is changed from the uplink or the time point when the uplink is switched to the downlink is called a switching point. Switch-point periodicity refers to a period in which an uplink subframe and a downlink subframe are repeatedly switched in the same manner, and both 5ms or 10ms are supported. In case of having a period of 5ms downlink-uplink switching time, the special subframe S exists every half-frame, and in case of having a period of 5ms downlink-uplink switching time, it exists only in the first half-frame.

In all configurations, subframes 0 and 5 and DwPTS are sections for downlink transmission only. The subframe immediately following the UpPTS and the subframe subframe is always an interval for uplink transmission.

The uplink-downlink configuration may be known to both the base station and the terminal as system information. When the uplink-downlink configuration information is changed, the base station may notify the terminal of the change of the uplink-downlink allocation state of the radio frame by transmitting only an index of the configuration information. In addition, the configuration information is a kind of downlink control information, which may be transmitted through a physical downlink control channel (PDCCH) like other scheduling information, and is commonly transmitted to all terminals in a cell through a broadcast channel as broadcast information. May be

Table 2 shows the configuration of the special subframe (length of DwPTS / GP / UpPTS).

The structure of a radio frame according to the example of FIG. 1 is just one example, and the number of subcarriers included in the radio frame or the number of slots included in the subframe and the number of OFDM symbols included in the slot may vary. Can be.

2 is a diagram illustrating a resource grid for one downlink slot in a wireless communication system to which the present invention can be applied.

Referring to FIG. 2, one downlink slot includes a plurality of OFDM symbols in the time domain. Here, one downlink slot includes seven OFDM symbols, and one resource block includes 12 subcarriers in a frequency domain, but is not limited thereto.

Each element on the resource grid is a resource element, and one resource block (RB) includes 12 × 7 resource elements. The number N ^ DL of resource blocks included in the downlink slot depends on the downlink transmission bandwidth.

The structure of the uplink slot may be the same as the structure of the downlink slot.

3 shows a structure of a downlink subframe in a wireless communication system to which the present invention can be applied.

Referring to FIG. 3, up to three OFDM symbols in the first slot in a subframe are control regions to which control channels are allocated, and the remaining OFDM symbols are data regions to which PDSCH (Physical Downlink Shared Channel) is allocated. data region). An example of a downlink control channel used in 3GPP LTE includes a physical control format indicator channel (PCFICH), a physical downlink control channel (PDCCH), a physical hybrid-ARQ indicator channel (PHICH), and the like.

The PCFICH is transmitted in the first OFDM symbol of a subframe and carries information about the number of OFDM symbols (ie, the size of the control region) used for transmission of control channels within the subframe. The PHICH is a response channel for the uplink and carries an ACK (Acknowledgement) / NACK (Not-Acknowledgement) signal for a hybrid automatic repeat request (HARQ). Control information transmitted through the PDCCH is called downlink control information (DCI). The downlink control information includes uplink resource allocation information, downlink resource allocation information or an uplink transmission (Tx) power control command for a certain terminal group.

The PDCCH is a resource allocation and transmission format of DL-SCH (Downlink Shared Channel) (also referred to as a downlink grant), resource allocation information of UL-SCH (Uplink Shared Channel) (also called an uplink grant), and PCH ( Paging information in paging channel, system information in DL-SCH, resource allocation for upper-layer control message such as random access response transmitted in PDSCH, arbitrary terminal It may carry a set of transmission power control commands for the individual terminals in the group, activation of Voice over IP (VoIP), and the like. The plurality of PDCCHs may be transmitted in the control region, and the terminal may monitor the plurality of PDCCHs. The PDCCH consists of a set of one or a plurality of consecutive CCEs. CCE is a logical allocation unit used to provide a PDCCH with a coding rate according to the state of a radio channel. The CCE corresponds to a plurality of resource element groups. The format of the PDCCH and the number of available bits of the PDCCH are determined according to the association between the number of CCEs and the coding rate provided by the CCEs.

The base station determines the PDCCH format according to the DCI to be transmitted to the terminal, and attaches a CRC (Cyclic Redundancy Check) to the control information. The CRC is masked with a unique identifier (referred to as RNTI (Radio Network Temporary Identifier)) according to the owner or purpose of the PDCCH. If the PDCCH for a specific terminal, a unique identifier of the terminal, for example, a C-RNTI (Cell-RNTI) may be masked to the CRC. Alternatively, if the PDCCH is for a paging message, a paging indication identifier, for example, P-RNTI (P-RNTI) may be masked to the CRC. If the system information, more specifically, the PDCCH for the system information block (SIB), the system information identifier and the system information RNTI (SI-RNTI) may be masked to the CRC. In order to indicate a random access response that is a response to the transmission of the random access preamble of the UE, a random access-RNTI (RA-RNTI) may be masked to the CRC.

4 shows a structure of an uplink subframe in a wireless communication system to which the present invention can be applied.

Referring to FIG. 4, an uplink subframe may be divided into a control region and a data region in the frequency domain. A physical uplink control channel (PUCCH) carrying uplink control information is allocated to the control region. The data region is allocated a Physical Uplink Shared Channel (PUSCH) that carries user data. In order to maintain a single carrier characteristic, one UE does not simultaneously transmit a PUCCH and a PUSCH.

A PUCCH for one UE is allocated a resource block (RB) pair in a subframe. RBs belonging to the RB pair occupy different subcarriers in each of the two slots. This RB pair allocated to the PUCCH is said to be frequency hopping at the slot boundary (slot boundary).

Reference signal (RS)

Since data is transmitted over a wireless channel in a wireless communication system, the signal may be distorted during transmission. In order to correctly receive the distorted signal at the terminal, the distortion of the received signal should be corrected using the channel information. In order to detect channel information, a signal transmission method known to both a transmitting side and a receiving side and a method of detecting channel information using a distorted degree when a signal is transmitted through a channel are mainly used. The above-mentioned signal is called a pilot signal or a reference signal (RS).

In addition, in recent years, when transmitting a packet in most mobile communication systems, a method of improving transmission and reception data efficiency by adopting a multiplexing antenna and a multiplexing antenna is avoided from using one transmitting antenna and one receiving antenna. use. When transmitting and receiving data using multiple input / output antennas, a channel state between a transmitting antenna and a receiving antenna must be detected in order to receive a signal accurately. Therefore, each transmit antenna must have a separate reference signal.

In a mobile communication system, RS can be classified into two types according to its purpose. There are RSs for channel information acquisition and RSs used for data demodulation. Since the former has a purpose for the UE to acquire channel information on the downlink, it should be transmitted over a wide band, and a UE that does not receive downlink data in a specific subframe should be able to receive and measure its RS. It is also used for measurements such as handover. The latter is an RS that the base station sends along with the corresponding resource when the base station transmits the downlink, and the UE can estimate the channel by receiving the RS, and thus can demodulate the data. This RS should be transmitted in the area where data is transmitted.

The downlink reference signal is one common reference signal (CRS: common RS) for acquiring information on channel states shared by all terminals in a cell, measurement of handover, etc. and a dedicated reference used for data demodulation only for a specific terminal. There is a signal (DRS: dedicated RS). Such reference signals may be used to provide information for demodulation and channel measurement. That is, DRS is used only for data demodulation and CRS is used for both purposes of channel information acquisition and data demodulation.

The receiving side (i.e., the terminal) measures the channel state from the CRS and transmits an indicator related to the channel quality such as the channel quality indicator (CQI), precoding matrix index (PMI) and / or rank indicator (RI). Feedback to the base station). CRS is also referred to as cell-specific RS. On the other hand, a reference signal related to feedback of channel state information (CSI) may be defined as CSI-RS.

The DRS may be transmitted through resource elements when data demodulation on the PDSCH is needed. The UE may receive the presence or absence of a DRS through a higher layer and is valid only when a corresponding PDSCH is mapped. The DRS may be referred to as a UE-specific RS or a demodulation RS (DMRS).

5 illustrates a reference signal pattern mapped to a downlink resource block pair in a wireless communication system to which the present invention can be applied.

Referring to FIG. 5, a downlink resource block pair may be represented by 12 subcarriers in one subframe × frequency domain in a time domain in a unit in which a reference signal is mapped. That is, one resource block pair on the time axis (x-axis) has a length of 14 OFDM symbols in case of normal cyclic prefix (normal CP) (in case of FIG. 5 (a)), and an extended cyclic prefix ( extended CP: Extended Cyclic Prefix) has a length of 12 OFDM symbols (in case of FIG. 5 (b)). The resource elements (REs) described as '0', '1', '2' and '3' in the resource block grid are determined by the CRS of the antenna port indexes '0', '1', '2' and '3', respectively. The location of the resource element described as 'D' means the location of the DRS.

Hereinafter, the CRS will be described in more detail. The CRS is used to estimate a channel of a physical antenna and is distributed in the entire frequency band as a reference signal that can be commonly received to all terminals located in a cell. That is, this CRS is a cell-specific signal and is transmitted every subframe for the wideband. In addition, the CRS may be used for channel quality information (CSI) and data demodulation.

CRS is defined in various formats depending on the antenna arrangement at the transmitting side (base station). In a 3GPP LTE system (eg, Release-8), RS for up to four antenna ports is transmitted according to the number of transmit antennas of a base station. The downlink signal transmitting side has three types of antenna arrangements such as a single transmit antenna, two transmit antennas, and four transmit antennas. For example, if the number of transmitting antennas of the base station is two, CRSs for antenna ports 0 and 1 are transmitted, and if four, CRSs for antenna ports 0 to 3 are transmitted.

If the base station uses a single transmit antenna, the reference signal for the single antenna port is arranged.

When the base station uses two transmit antennas, the reference signals for the two transmit antenna ports are arranged using time division multiplexing (TDM) and / or FDM frequency division multiplexing (FDM) scheme. That is, the reference signals for the two antenna ports are assigned different time resources and / or different frequency resources so that each is distinguished.

In addition, when the base station uses four transmit antennas, reference signals for the four transmit antenna ports are arranged using the TDM and / or FDM scheme. The channel information measured by the receiving side (terminal) of the downlink signal may be transmitted by a single transmit antenna, transmit diversity, closed-loop spatial multiplexing, open-loop spatial multiplexing, or It may be used to demodulate data transmitted using a transmission scheme such as a multi-user MIMO.

When a multiple input / output antenna is supported, when a reference signal is transmitted from a specific antenna port, the reference signal is transmitted to a location of resource elements specified according to a pattern of the reference signal, and the location of resource elements specified for another antenna port. Is not sent to. That is, reference signals between different antennas do not overlap each other.

The rules for mapping CRSs to resource blocks are defined as follows.

은 하나의 하향링크 슬롯에서의 OFDM 심볼의 수를 나타내고,

은 하향링크에 할당된 무선 자원의 수를 나타낸다. n_s는 슬롯 인덱스를 나타내고,

은 셀 ID를 나타낸다. mod 는 모듈로(modulo) 연산을 나타낸다. 참조 신호의 위치는 주파수 영역에서 v_shift 값에 따라 달라진다. v_shift는 셀 ID에 종속되므로, 참조 신호의 위치는 셀에 따라 다양한 주파수 편이(frequency shift) 값을 가진다.In Equation 1, k and l represent a subcarrier index and a symbol index, respectively, and p represents an antenna port.

Denotes the number of OFDM symbols in one downlink slot,

Represents the number of radio resources allocated to the downlink. n _s represents the slot index,

Represents a cell ID. mod stands for modulo operation. The position of the reference signal depends on the v _shift value in the frequency domain. Since v _shift is dependent on the cell ID, the position of the reference signal has various frequency shift values according to the cell.

More specifically, the position of the CRS may be shifted in the frequency domain according to the cell in order to improve channel estimation performance through the CRS. For example, when reference signals are located at intervals of three subcarriers, reference signals in one cell are allocated to the 3k th subcarrier, and reference signals in another cell are allocated to the 3k + 1 th subcarrier. In terms of one antenna port, the reference signals are arranged at six resource element intervals in the frequency domain, and are separated at three resource element intervals from the reference signal allocated to another antenna port.

In the time domain, reference signals are arranged at constant intervals starting from symbol index 0 of each slot. The time interval is defined differently depending on the cyclic prefix length. In the case of the normal cyclic prefix, the reference signal is located at symbol indexes 0 and 4 of the slot, and in the case of the extended cyclic prefix, the reference signal is located at symbol indexes 0 and 3 of the slot. The reference signal for the antenna port having the maximum value of two antenna ports is defined in one OFDM symbol. Thus, for four transmit antenna transmissions, the reference signals for reference signal antenna ports 0 and 1 are located at symbol indices 0 and 4 (symbol indices 0 and 3 for extended cyclic prefix) of slots, The reference signal for is located at symbol index 1 of the slot. The positions in the frequency domain of the reference signal for antenna ports 2 and 3 are swapped with each other in the second slot.

In more detail with respect to DRS, DRS is used to demodulate data. Precoding weights used for a specific terminal in multiple I / O antenna transmission are used without change to estimate the corresponding channel by combining with the transmission channel transmitted from each transmission antenna when the terminal receives the reference signal.

The 3GPP LTE system (eg, Release-8) supports up to four transmit antennas and a DRS for rank 1 beamforming is defined. The DRS for rank 1 beamforming also indicates a reference signal for antenna port index 5.

The rules for mapping DRS to resource blocks are defined as follows. Equation 2 shows a case of a general cyclic transpose, and Equation 3 shows a case of an extended cyclic transpose.

은 주파수 영역에서 자원 블록 크기를 나타내고, 부반송파의 수로써 표현된다. n_PRB은 물리 자원 블록의 수를 나타낸다.

은 PDSCH 전송을 위한 자원 블록의 주파수 대역을 나타낸다. n_s는 슬롯 인덱스를 나타내고,

는 셀 ID를 나타낸다. mod 는 모듈로(modulo) 연산을 나타낸다. 참조 신호의 위치는 주파수 영역에서 v_shift 값에 따라 달라진다. v_shift는 셀 ID에 종속되므로, 참조 신호의 위치는 셀에 따라 다양한 주파수 편이(frequency shift) 값을 가진다.In Equations 2 and 3, k and l represent subcarrier indexes and symbol indexes, respectively, and p represents an antenna port.

Denotes the resource block size in the frequency domain and is expressed as the number of subcarriers. n _PRB represents the number of physical resource blocks.

Denotes a frequency band of a resource block for PDSCH transmission. n _s represents the slot index,

Represents a cell ID. mod stands for modulo operation. The position of the reference signal depends on the v _shift value in the frequency domain. Since v _shift is dependent on the cell ID, the position of the reference signal has various frequency shift values according to the cell.

LTE system evolution In the advanced LTE-A system, it should be designed to support up to eight transmit antennas in the downlink of the base station. Therefore, RS for up to eight transmit antennas must also be supported. Since the downlink RS in the LTE system defines only RSs for up to four antenna ports, when the base station has four or more up to eight downlink transmit antennas in the LTE-A system, RSs for these antenna ports are additionally defined. Must be designed. RS for up to eight transmit antenna ports must be designed for both the RS for channel measurement and the RS for data demodulation described above.

One of the important considerations in designing the LTE-A system is backward compatibility, that is, the LTE terminal must work well in the LTE-A system, and the system must also support it. From an RS transmission point of view, an RS for an additional up to eight transmit antenna ports should be additionally defined in the time-frequency domain in which CRS defined in LTE is transmitted every subframe over the entire band. In the LTE-A system, when RS patterns of up to eight transmit antennas are added to all bands in every subframe in the same manner as the CRS of the existing LTE, the RS overhead becomes excessively large.

Accordingly, the newly designed RS in the LTE-A system is divided into two categories, RS for channel measurement purpose (CSI-RS: Channel State Information-RS, Channel State Indication-RS, etc.) for selection of MCS, PMI, etc. ) And RS (Data Demodulation-RS) for data demodulation transmitted through eight transmit antennas.

CSI-RS for the purpose of channel measurement has a feature that is designed for channel measurement-oriented purposes, unlike the conventional CRS is used for data demodulation at the same time as the channel measurement, handover, and the like. Of course, this may also be used for the purpose of measuring handover and the like. Since the CSI-RS is transmitted only for obtaining channel state information, unlike the CRS, the CSI-RS does not need to be transmitted every subframe. In order to reduce the overhead of the CSI-RS, the CSI-RS is transmitted intermittently on the time axis.

DMRS is transmitted to the UE scheduled in the corresponding time-frequency domain for data demodulation. That is, the DM-RS of a specific UE is transmitted only in a region where the UE is scheduled, that is, a time-frequency region in which data is received.

In the LTE-A system, the eNB should transmit CSI-RS for all antenna ports. Transmitting CSI-RS for each subframe for up to 8 transmit antenna ports has a disadvantage in that the overhead is too large. Therefore, the CSI-RS is not transmitted every subframe but is transmitted intermittently on the time axis. Can be reduced. That is, the CSI-RS may be periodically transmitted with an integer multiple of one subframe or may be transmitted in a specific transmission pattern. At this time, the period or pattern in which the CSI-RS is transmitted may be set by the eNB.

In order to measure the CSI-RS, the UE must transmit the CSI-RS index of the CSI-RS for each CSI-RS antenna port of the cell to which it belongs, and the CSI-RS resource element (RE) time-frequency position within the transmitted subframe. , And information about the CSI-RS sequence.

 In the LTE-A system, the eNB should transmit CSI-RS for up to eight antenna ports, respectively. Resources used for CSI-RS transmission of different antenna ports should be orthogonal to each other. When one eNB transmits CSI-RSs for different antenna ports, these resources may be orthogonally allocated in FDM / TDM manner by mapping CSI-RSs for each antenna port to different REs. Alternatively, the CSI-RSs for different antenna ports may be transmitted in a CDM scheme that maps to orthogonal codes.

When the eNB informs its cell UE of the information about the CSI-RS, it is necessary to first inform the information about the time-frequency to which the CSI-RS for each antenna port is mapped. Specifically, the subframe numbers through which the CSI-RS is transmitted, or the period during which the CSI-RS is transmitted, the subframe offset through which the CSI-RS is transmitted, and the OFDM symbol number where the CSI-RS RE of a specific antenna is transmitted, and the frequency interval (spacing), the RE offset or shift value in the frequency axis.

Communication system using ultra high frequency band

In LTE (Long Term Evolution) / LTE-A (LTE Advanced) system, the error value of the oscillator of the terminal and the base station is defined as a requirement, and is described as follows.

UE side frequency error (in TS 36.101)

The UE modulated carrier frequency shall be accurate to within ± 0.1 PPM observed over a period of one time slot (0.5 ms) compared to the carrier frequency received from the E-UTRA Node B

eNB side frequency error (in TS 36.104)

Frequency error is the measure of the difference between the actual BS transmit frequency and the assigned frequency.

Meanwhile, the oscillator accuracy according to the type of base station is shown in Table 3 below.

Therefore, the maximum difference of the oscillator between the base station and the terminal is ± 0.1ppm, and when an error occurs in one direction, a maximum offset value of 0.2 ppm may occur. This offset value is multiplied by the center frequency and converted into Hz units for each center frequency.

On the other hand, in the OFDM system, the CFO value appears differently according to the frequency tone interval, and in general, even if the large CFO value has a relatively small effect on the OFDM system with a sufficiently large frequency tone interval. Therefore, the actual CFO value (absolute value) needs to be expressed as a relative value affecting the OFDM system, which is called a normalized CFO. The normalized CFO is expressed as the CFO value divided by the frequency tone interval. Table 4 below shows the CFO and normalized CFO for each center frequency and oscillator error value.

In Table 4, the frequency tone interval (15 kHz) is assumed for the center frequency of 2 GHz (for example, LTE Rel-8 / 9/10), and the frequency tone interval is 104.25 kHz for the center frequency of 30 GHz and 60 GHz. This prevents performance degradation considering the Doppler effect for each center frequency. Table 2 above is a simple example and it is obvious that other frequency tone spacings may be used for the center frequency.

로 표현될 수 있다. 이때, v는 단말의 이동 속도이며, λ는 전송되는 전파의 중심 주파수의 파장을 의미한다. θ는 수신되는 전파와 단말의 이동 방향 사이의 각도를 의미한다. 이하에서는 θ가 0인 경우를 전제로 하여 설명한다. On the other hand, in a situation where the terminal moves at a high speed or in a high frequency band, a Doppler spread phenomenon greatly occurs. Doppler dispersion causes dispersion in the frequency domain, resulting in distortion of the received signal at the receiver's point of view. Doppler dispersion

It can be expressed as. In this case, v is the moving speed of the terminal, and λ means the wavelength of the center frequency of the transmitted radio waves. θ means the angle between the received radio wave and the moving direction of the terminal. The following description is based on the assumption that θ is zero.

로 표현된다. 무선 통신 시스템에서는 도플러 분산에 대한 수식과 코히어런스 타임에 대한 수식 간의 기하 평균(geometric mean)을 나타내는 아래의 수학식 4가 주로 이용된다.In this case, the coherence time is in inverse proportion to the Doppler variance. If the coherence time is defined as a time interval in which the correlation value of the channel response in the time domain is 50% or more,

It is expressed as In the wireless communication system, Equation 4 below, which represents a geometric mean between the equation for Doppler variance and the equation for coherence time, is mainly used.

6 shows an example of a resource area structure used in a communication system using mmWave to which the present invention can be applied.

A communication system using an ultra high frequency band such as mmWave uses a frequency band different in physical properties from the conventional LTE / LTE-A communication system. Accordingly, in a communication system using an ultra high frequency band, a resource structure of a form different from that of the resource region used in the conventional communication system is being discussed. 6 shows an example of a downlink resource structure of a new communication system.

Considering a resource block (RB pair) consisting of 14 Orthogonal Frequency Division Multiplexing (OFDM) symbols on the horizontal axis and 12 frequency tones on the vertical axis, the first two (or three) OFDM symbols 1310 Is assigned to a control channel (for example, a physical downlink control channel (PDCCH)), and the next one to two OFDM symbols 620 are assigned a DeModulation Reference Signal (DMRS), and the remaining OFDM symbols ( The 630 may be allocated a data channel (eg, a physical downlink shared channel (PDSCH)).

Meanwhile, in the resource region structure as shown in FIG. 6, the PCRS or PNRS or PTRS for CPE (or CFO) estimation described above may be carried on a part of a resource element (RE) of the region 630 to which the data channel is allocated and transmitted to the terminal. Such a signal is a signal for estimating phase noise, and may be a pilot signal as described above or a signal whose data signal is changed or duplicated.

The present invention proposes a method of transmitting DMRS for channel estimation in downlink or uplink.

7 and 8 illustrate an example of a pattern of a demodulation reference signal proposed in the present specification.

7 and 8, a demodulation reference signal for estimating a channel may be mapped to one symbol or two symbols according to the maximum number of antenna ports.

In detail, the uplink DMRS and the downlink DMRS may be generated and mapped to the resource region by the following method. FIG. 7 illustrates an example of an uplink or downlink DMRS mapped to a physical resource according to type 1, and FIG. 8 illustrates an example of an uplink or downlink DMRS mapped to a physical resource according to type 2. FIG.

Demodulation reference signal for PUSCH

The reference signal sequence r (m) for generating the downlink DMRS is generated by Equation 5 below when transform precoding for a PUSCH is not allowed.

In this case, an example of a case where transform precoding for a PUSCH is not allowed may be a case of generating a transmission signal of a CP-OFDM scheme.

Here, c (i) means the pseudo-random sequence.

If transform precoding for the PUSCH is allowed, the reference signal sequence r (m) is generated by Equation 6 below.

In this case, an example of a case where transform precoding for a PUSCH is allowed may be a case where a transmission signal of a DFT-S-OFDM scheme is generated.

The DMRS of the generated PUSCH is mapped to a physical resource according to Type 1 or Type 2 given by higher layer parameters as shown in FIGS. 8 and 9.

In this case, the DMRS may be mapped to a single symbol or a double symbol according to the number of antenna ports.

If transform precoding is not allowed, the reference signal sequence r (m) may be mapped to a physical resource by Equation 7 below.

,

, 및 △는 아래 표 5 및 표 6에 의해서 주어진다.In Equation 7, l is defined relative to the start of the PUSCH transmission.

,

, And Δ are given by Tables 5 and 6 below.

Table 5 below shows an example of parameters for DMRS of the PUSCH for Type 1.

Table 6 below shows an example of parameters for DMRS of a PUSCH for type 2. FIG.

Table 7 below shows an example of the time domain index l 'and the supported antenna port p according to the higher layer parameter UL_DMRS_dur.

의 일 예를 나타낸다.Table 8 below shows the starting position of DMRS of PUSCH.

An example is shown.

Demodulation reference signals for PDSCH

A reference signal sequence r (m) for generating downlink DMRS is generated by Equation 8 below.

Here, c (i) means the pseudo-random sequence.

The DMRS of the generated PDSCH is mapped to a physical resource according to the type 1 or type 2 given by higher layer parameters as shown in FIGS. 8 and 9.

In this case, the reference signal sequence r (m) may be mapped to a physical resource by Equation 9 below.

,

, 및 △는 아래 표 11 및 표 12에 의해서 주어진다.In Equation 9, l is defined relative to the beginning of a slot.

,

, And Δ are given by Tables 11 and 12 below.

값은 매핑 유형에 따라 표 13에서 주어진 상위 계층 매개 변수 DL_DMRS_add_pos에 따라 달라진다.The time axis index | 'and supporting antenna ports p depend on the higher layer parameter DL_DMRS_dur according to Table 12 below.

The value depends on the upper layer parameter DL_DMRS_add_pos given in Table 13, depending on the mapping type.

For PDSCH mapping type A: if the upper layer parameter DL_DMRS_typeA_pos is equal to 3, l ₀ = 3, otherwise l ₀ = 2.

For PDSCH mapping type B: l ₀ is mapped to the first OFDM symbol in the PDSCH resource for which DMRS is scheduled.

Table 9 below shows an example of parameters for DMRS configuration type 1 of the PDSCH.

Table 10 below shows an example of parameters for DMRS configuration type 2 of the PDSCH.

Table 11 below shows an example of l ′, which is a duration of PDSCH DMRS.

의 일 예를 나타낸다.Table 12 below shows the starting position of DMRS of PDSCH.

An example is shown.

In the NR system, as described above, DMRS is defined in units of OFDM symbols. In order to support the fast decoding speed, the DMRS is placed in the front symbol of the slot.

The DMRS located at the front symbol of the slot may be called a front-loaded DMRS.

In the present invention, the DMRS located in the front symbol of the slot is called a first DMRS or a front-loaded DMRS for fast decoding. However, in the case of the High Doppler environment, since channel variation is large in one slot (or subframe), it is difficult to properly compensate the channel using only the DMRS set in the front symbol.

Accordingly, in order to solve this problem, additional DMRSs can be set. In the present invention, such DMRSs are referred to as second DMRSs or additional DMRSs.

9 to 13 are diagrams illustrating an example of a method of mapping DMRSs using a repeating pattern proposed herein.

9 to 13, when the number of antenna ports used for transmitting the DMRS is a predetermined number or more, the base station may repeat the same mapping pattern to map the DMRS to resources.

9 and 10 show examples of DMRS mapping patterns for supporting up to 8 DMRS ports. 9 (a) to 9 (c) show an example of a mapping pattern for mapping DMRSs using one OFDM symbol, and FIGS. 10 (a) to 10 (c) show DMRSs using two OFDM symbols. An example of a mapping pattern to map is shown.

Specifically, (a) to (b) of FIG. 9 show an example of supporting eight DMRS ports using FDM using two different resources and CDM in a frequency domain corresponding to length 4.

On the other hand, Figure 9 (c) shows an example of supporting the 8 DMRS port using the FDM using four different resources and the CDM of the frequency domain corresponding to the length 2.

FIG. 10A illustrates an example of supporting 8 DMRS ports using FDM using four different resources and a CDM in a time domain of length 2. Referring to FIG. 10 (b) shows an example of supporting eight DMRS ports using FDM and TDM using two different resources and CDM in a frequency domain corresponding to length 2. FIG.

10C illustrates an example of mapping DMRSs using a repeating pattern of repeating the same pattern.

In FIG. 10 (c), the DMRS mapping pattern is composed of two OFDM symbols, but in fact, eight DMRS ports are configured in one OFDM symbol and have a repetitive structure using the same.

Specifically, eight DMRS ports may be supported by CDM in a frequency domain corresponding to length 4 and FDM using two different resources.

Hereinafter, (a) of FIG. 9 is a pattern 5, (b) is a pattern 6, (c) is a pattern 7, (a) is a pattern 8, (b) is a pattern 9, and (c) is a pattern 10. Call it.

FIG. 11 is a diagram illustrating an example of spectral efficiency performance for each mapping pattern of FIGS. 9 and 10.

As shown in FIG. 11, in the case of supporting eight DMRS ports, better SE performance is obtained compared to the mapping pattern composed of one OFDM symbol in pattern 8 and pattern 10 constituting the mapping pattern using two OFDM symbols. It can be seen that indicates.

In this case, in the case of pattern 9 using two OFDM symbols, it can be seen that performance is deteriorated similarly to a pattern composed of one OFDM symbol.

This can be inferred that the pattern 9 uses TDM because the energy of the reference signal is smaller than that of other patterns using two OFDM symbols.

That is, in the case of the pattern 8 and the pattern 10, since the DMRSs are mapped by using two OFDM symbols for eight ports, the RS energy can be increased, thereby gaining channel coefficient estimation.

In addition, although the inter-layer interference is reduced due to the gain of the channel coefficient estimation, the performance may be improved in terms of the SE even though the RS overhead is increased.

At this time, among the pattern 8 and the pattern 10 using two OFDM symbols, the pattern 10 may be a mapping pattern that is more suitable for a high carrier frequency (mmWave) band with a large influence of phase noise.

Specifically, in the case of pattern 8, the CDM of the time domain is used. However, when a phase difference occurs between adjacent OFDM symbols due to the influence of phase noise, performance may be degraded in the case of a pattern using a CDM in a time domain that assumes the same channel between adjacent OFDM symbols as shown in pattern 8.

On the other hand, in the case of pattern 10, since it is a repetitive structure using the same pattern between adjacent OFDM symbols, an error due to phase noise can be estimated and compensated for. In detail, by estimating a phase difference between adjacent OFDM symbols, and estimating a channel by compensating the estimated phase difference, an error that may cause degradation in channel estimation performance may be compensated in advance.

Therefore, when the number of antenna ports for transmitting the DMRS exceeds a certain number, the DMRS may be mapped to a resource using a repetition pattern.

Specifically, when the number of antenna ports for DMRS transmission is more than a certain number, the base station may increase the CDM length in the frequency domain and repeatedly use the same pattern in the time domain.

In another embodiment of the present invention, the mapping pattern of the DMRS may be determined according to the transmission frequency.

In detail, in the high frequency band, degradation of CDM performance in the time domain may occur due to the influence of phase noise. Therefore, a repetition pattern that can estimate and compensate for CPE due to phase noise in the high frequency band and provide sufficient RS energy to improve channel estimation performance can be prioritized.

For example, if the maximum number of antenna ports is 12, the DMRS may be mapped as shown in FIG.

That is, a mapping pattern configured to support up to 12 DMRS ports in one OFDM symbol may be defined to be repeated in an adjacent OFDM symbol.

In the above example, the CDM length in the frequency domain has been increased to support the number of DMRS ports in one OFDM symbol. In the case of a channel with a long delay spread, channel estimation performance may be degraded due to a channel having a high frequency selectivity.

However, in the high frequency band, propagation characteristics such as large path attenuation, strong straightness, and small transmittance are not good. In addition, because they are used with beamforming technology to compensate for large path attenuation, channels in the high frequency band have a small delay spread. Accordingly, the DMRS pattern having a repeating structure may be referred to as a mapping pattern suitable for a high frequency band.

Therefore, the channel estimation performance can be improved according to the frequency band by determining the transmission frequency band and the DMRS pattern which can be preferred in the frequency band.

According to another embodiment of the present invention, whether to apply the CDM in the time domain according to the CDM length in the frequency domain or limit the type of OCC code applied to the CDM in the time domain.

For example, as shown in (a) of FIG. 10, eight DMRS ports may be supported using CDM in a time domain corresponding to length 2 and FDM using four different resources. On the other hand, to support the same eight DMRS ports, as shown in (c) of FIG. 10, a repetition pattern including a CDM in a frequency domain corresponding to length 4 and FDM using two different resources may be used.

In the high frequency region, the phase noise affects the channel estimation performance due to the effect of phase noise. Therefore, in the case of the high frequency region, the phase noise of the CDM length is long and repeats among the two mapping patterns supporting the eight DMRS ports described above, that is, the pattern shown in FIG. It can estimate the impact and compensate for it in the channel estimation.

As in the above example, whether the CDM is applied in the time domain or the DMRS mapping pattern may vary according to the CDM length in the frequency domain. As such, the base station may set the DMRS mapping pattern and whether the CDM is applied to the time domain based on the CDM length of the frequency domain.

When the DMRS is mapped using the repetition pattern, whether the pattern is repeated may be represented by CDM on / off of the time domain or by restriction of an OCC code applied to the CDM.

For example, when the CDM of length 3 is applied to the frequency domain and the CDM of length 2 is applied to the time domain, as shown in FIG. 13A, the OCC code of length 2 used in the time domain is [ +1, +1], [+1, -1].

In this case, the number of ports multiplexed in the DMRS pattern may be 12 ports in total. However, when only one OCC code in the time domain is used, multiplexing of 6 ports is possible.

In this case, when the restriction is made to use only OCC codes [+1, +1], the same effect as using a repeating pattern can be obtained.

That is, as shown in FIG. 13A, when the CDM length is 3 in the frequency domain, a total of 12 ports may be multiplexed using the OCC code having the length 2 in the time domain.

At this time, when the CDM length in the frequency domain is 4 or more, as shown in FIGS. 13B and 13C, the same effect as using the repeating pattern is generated by turning off the CDM in the time domain or limiting the type of OCC code to one. You can.

In this case, the base station explicitly sets the restriction on whether CDM is applied in the time domain or the type of OCC code applied to the CDM through at least one of higher layer signaling (eg, RRC, MAC CE, etc.) or DCI. You can let them know.

Alternatively, the base station may inform the CDM length of the frequency domain through at least one of higher layer signaling or DCI, and the terminal may apply the CDM to the time domain based on the CDM length transmitted from the base station or the OCC code applied to the CDM. Restrictions can be recognized.

In another embodiment of the present invention, the base station may inform the terminal of the type of OCC code applied to the CDM in the time domain or the CDM on / off in the time domain through higher layer signaling or DCI.

For example, the base station can inform the terminal of the OCC length in the time domain through the phy layer or DCI directly.

In this case, if there is no restriction on the time domain OCC code, a total of 12 ports should be supported, but if there is a limit, only a total of 6 ports will be supported, thereby reducing the amount of information to be displayed.

When the UE informs such information, since the UE can recognize whether the OCC code of the DMRS pattern is limited, the UE can estimate the CPE and the CFO and then receive the DMRS that compensates for the estimated value.

If the base station does not explicitly inform the UE of the type of OCC code applied to the CDM in the time domain or whether the CDM is on or off in the time domain, the UE is for estimating the phase error due to transmission frequency and phase noise. It may be assumed that MU pairing with other UEs having different OCC codes in the time domain is based on PTRS transmission, MCS, or number of layers.

When the UE satisfies the proposed hypothesis, the UE may perform a receiving operation of compensating a phase difference between DMRS symbols due to CPEs appearing in each DMRS and then performing combining of contiguous DMRS symbols.

For example, when the UE uses a transmission frequency of the mmWave band and the MCS uses 256QAM, a process of combining the concatenated DMRSs after compensating for the phase difference between contiguous DMRS symbols may be performed.

Even if there is no explicit signaling as in the example of the proposal, the base station may schedule to use only the same OCC code in the time domain by using other information delivered to the terminal.

In this case, assuming that the UE is not MU paired in a specific environment, it is possible to receive the DMRS, thereby preventing degradation due to phase noise and performing channel estimation.

14 is a flowchart illustrating an example of a method for generating and transmitting a demodulation reference signal proposed in the present specification.

Referring to FIG. 14, the base station generates a reference signal sequence based on a pseudo random sequence (S14010). In this case, the demodulation reference signal may be the front-loaded DMRS described above.

Thereafter, the base station maps the generated reference signal sequence to one or two time axis symbols according to a specific pattern (S14020). In this case, the base station may map a reference signal sequence generated according to a specific pattern to one or two time axis symbols, and the specific pattern may be one of the patterns described with reference to FIGS. 7 to 13.

The specific pattern may be determined according to the characteristics of the frequency band in which the demodulation reference signal is transmitted.

As shown in FIGS. 7 to 13, the demodulation reference signal may be multiplexed and mapped to one or two time axis symbols through the CDM on the frequency axis and / or the time axis.

At this time, the CDM applied on the time axis is called the first CDM, and the CDM applied on the frequency axis is called the second CDM.

Thereafter, the base station generates a demodulation reference signal based on the mapping of one or two time axis symbols, and transmits the generated demodulation reference signal to the terminal using different antenna ports (S14030 and S14040).

In this case, the demodulation reference signal sequence is mapped on the same time axis symbol and transmitted on a specific antenna port, respectively, and the demodulation reference signal may be located on the same time axis symbol as at least one other demodulation reference signal transmitted on another antenna port. have.

15 is a flowchart illustrating an example of a method of decoding data by receiving a demodulation reference signal proposed in the present specification.

Referring to FIG. 15, a terminal receives a demodulation reference signal (DMRS) set according to a specific pattern from a base station from a base station through a DMRS symbol (S15010).

The demodulation reference signal is transmitted on a specific antenna port and may be located on the same one or two time axis symbols as at least one other demodulation reference signal transmitted on another antenna port.

In addition, the demodulation reference signal may be multiplexed and mapped to one or two time axis symbols through a CDM on a frequency axis and / or a time axis as described with reference to FIGS. 7 to 13.

At this time, the CDM applied on the time axis is called the first CDM, and the CDM applied on the frequency axis is called the second CDM.

The specific pattern may be one of the patterns described with reference to FIGS. 7 to 13, and may be determined according to characteristics of a frequency band in which a demodulation reference signal is transmitted.

Thereafter, the terminal may decode the data using the received demodulation reference signal (S15020).

16 is a diagram illustrating an example of an internal block diagram of a wireless device to which the present invention can be applied.

Here, the wireless device may be a base station and a terminal, and the base station includes both a macro base station and a small base station.

As illustrated in FIG. 16, the base station 1610 and the UE 1620 include a communication unit (transmitter and receiver, RF unit, 1613 and 1623), a processor 1611 and 1621, and a memory 1612 and 1622.

In addition, the base station and the UE may further include an input unit and an output unit.

The communication units 1613 and 1623, the processors 1611 and 1621, the input unit, the output unit, and the memory 1612 and 1622 are functionally connected to perform the method proposed herein.

When the communication unit (transmitter / receiver unit or RF unit, 1613, 1623) receives information generated from the PHY protocol (Physical Layer Protocol), the received information is transferred to the RF-Radio-Frequency Spectrum, filtered, and amplified. ) To transmit to the antenna. In addition, the communication unit functions to move an RF signal (Radio Frequency Signal) received from the antenna to a band that can be processed by the PHY protocol and perform filtering.

The communication unit may also include a switch function for switching the transmission and reception functions.

Processors 1611 and 1621 implement the functions, processes and / or methods proposed herein. Layers of the air interface protocol may be implemented by a processor.

The processor may be represented by a controller, a controller, a control unit, a computer, or the like.

The memories 1612 and 1622 are connected to a processor and store protocols or parameters for performing an uplink resource allocation method.

Processors 1611 and 1621 may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and / or other storage device. The communication unit may include a baseband circuit for processing a wireless signal. When the embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function.

The module may be stored in memory and executed by a processor. The memory may be internal or external to the processor and may be coupled to the processor by various well known means.

The output unit (display unit or display unit) is controlled by a processor and outputs information output from the processor together with a key input signal generated at the key input unit and various information signals from the processor.

Further, for convenience of description, the drawings are divided and described, but it is also possible to design a new embodiment by merging the embodiments described in each drawing. And, according to the needs of those skilled in the art, it is also within the scope of the present invention to design a computer-readable recording medium having a program recorded thereon for executing the embodiments described above.

The method for transmitting and receiving the reference signal according to the present specification is not limited to the configuration and method of the embodiments described as described above, the embodiments are all or part of each embodiment so that various modifications can be made May be optionally combined.

On the other hand, the method for transmitting and receiving the reference signal of the present specification can be implemented as a processor-readable code on a processor-readable recording medium provided in the network device. The processor-readable recording medium includes all kinds of recording devices that store data that can be read by the processor. Examples of the processor-readable recording medium include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage device, and the like, and may also be implemented in the form of a carrier wave such as transmission over the Internet. . The processor-readable recording medium can also be distributed over network coupled computer systems so that the processor-readable code is stored and executed in a distributed fashion.

In addition, while the above has been shown and described with respect to preferred embodiments of the present specification, the present specification is not limited to the specific embodiments described above, the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

In addition, in this specification, both the object invention and the method invention are described, and description of both invention can be supplementally applied as needed.

The RRC connection method in the wireless communication system of the present invention has been described with reference to an example applied to the 3GPP LTE / LTE-A system, but it is possible to apply to various wireless communication systems in addition to the 3GPP LTE / LTE-A system.

Claims (16)

In the method for the terminal to decode (Decoding) data in a wireless communication system,
Receiving a demodulation reference signal (DMRS) set according to a specific pattern from a base station from a base station through a DMRS symbol,
The demodulation reference signal is transmitted on a specific antenna port, and is located on the same one or two time axis symbols as at least one other demodulation reference signal transmitted on another antenna port,
The demodulation reference signal is mapped to the one or two time axis symbols using at least one of a first code division multiplexing (CDM) on a frequency axis or a second CDM on a time axis,
The specific pattern is determined according to a characteristic of a frequency band in which the demodulation reference signal is transmitted; And
Decoding the data using the demodulation reference signal. The method of claim 1,
Wherein said demodulation reference signal is located on said one or two time axis symbols based on at least one of a number of transport layers, a port index, a rank, or a maximum number of transport ports. The method of claim 1,
And when the demodulation reference signal is located on one time axis symbol, the demodulation reference signal is mapped using the first CDM. The method of claim 1,
If the demodulation reference signal is located on two time axis symbols, the demodulation reference signal is mapped using the second CDM. The method of claim 1,
Receiving a signal indicating whether the second CDM is applied from the base station;
And if the signal indicates application of the second CDM, then the demodulation reference signal is mapped using the first CDM and the second CDM. The method of claim 1,
When the first CDM is applied, further comprising the step of receiving a signal indicating the length of the first CDM from the base station,
Whether to apply the second CDM is determined according to the length of the first CDM. The method of claim 1,
When the demodulation reference signal is mapped using the first CDM and the second CDM, an orthogonal cover code (OCC) applied to the second CDM is limited to at least one type by the base station. How to be. The method of claim 1,
When a phase tacking reference signal (PTRS) for phase estimation is transmitted, the demodulation reference signal is mapped to the one or two time axis symbols through the first code division multiplexing (CDM). A terminal for decoding data in a wireless communication system,
A radio unit for transmitting and receiving radio signals to and from the outside; And
A processor is functionally coupled to the wireless unit, wherein the processor includes:
A demodulation reference signal (DMRS) set according to a specific pattern from the base station is received from the base station through a DMRS symbol,
The demodulation reference signal is transmitted on a specific antenna port, and is located on the same one or two time axis symbols as at least one other demodulation reference signal transmitted on another antenna port,
The demodulation reference signal is mapped to the one or two time axis symbols using at least one of a first code division multiplexing (CDM) on a frequency axis or a second CDM on a time axis,
The specific pattern is determined according to the characteristics of the frequency band in which the demodulation reference signal is transmitted,
And a terminal for decoding the data using the demodulation reference signal. The method of claim 9,
The demodulation reference signal is located on the one or two time axis symbols based on at least one of a number of transport layers, a port index, a rank, or a maximum number of transport ports. The method of claim 9,
When the demodulation reference signal is located on one time axis symbol, the demodulation reference signal is mapped using the first CDM. The method of claim 9,
If the demodulation reference signal is located on two time axis symbols, the demodulation reference signal is mapped using the second CDM. The method of claim 9, wherein the processor,
Receive a signal indicating whether the second CDM is applied from the base station,
The demodulation reference signal is mapped using the first CDM and the second CDM when the signal indicates the application of the second CDM. The method of claim 9,
When the first CDM is applied, receiving a signal indicating the length of the first CDM from the base station,
Whether to apply the second CDM is determined according to the length of the first CDM. The method of claim 9,
When the demodulation reference signal is mapped using the first CDM and the second CDM, an orthogonal cover code (OCC) applied to the second CDM is limited to at least one type by the base station. Terminal. The method of claim 9,
When a phase tacking reference signal (PTRS) for phase estimation is transmitted, the demodulation reference signal is mapped to the one or two time axis symbols through the first code division multiplexing (CDM).

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